Educational reference only. Not medical advice. Consult a healthcare provider before starting any protocol.
Thymosin Beta-4
Thymosin Beta-4 (Tβ4 / Timbetasin)
What it is
The full-length 43-amino-acid endogenous polypeptide encoded by the TMSB4X gene. Thymosin Beta-4 is the most abundant G-actin-sequestering protein in mammalian cells and has been studied in Phase 1–3 human trials for wound healing, corneal repair, and cardiac recovery. It contains multiple functional domains — including the central LKKTETQ actin-binding motif (the basis for the TB-500 fragment, which is a separate database entry) and the N-terminal Ac-SDKP anti-fibrotic tetrapeptide. Unlike TB-500, the full-length protein retains all known bioactive regions. RegeneRx/ReGenTree's ophthalmic formulation (RGN-259) holds FDA orphan drug designation for neurotrophic keratitis.
Community-reported ranges
Dose ranges sourced from community forums and published Phase 1–2 clinical trial protocols. Not dosing guidance.
Reported dose range
2000–2500 mcg
Estimated half-life
~2-3 days (subcutaneous, estimated)
Source: community estimate; formal SubQ PK not published. IV PK showed dose-proportional kinetics in Phase 1 (Ruff et al., 2010).
Reported cycle length
6–8 weeks on
4-6 weeks off
Route
subcutaneous
Common vial sizes
2mg, 5mg, 10mg
Reported timing
AM, 2-3x/week (loading phase: 4-8mg/week total; maintenance: 2-4mg every 1-2 weeks)
Reported frequency
2-3x weekly
Frequently discussed alongside
Based on community forum discussions. Not a recommendation to combine compounds.
Published research
Thymosin Beta-4 has one of the most advanced clinical programs among tissue-repair peptides. A Phase 1 safety study in 40 healthy volunteers (Ruff et al., 2010) demonstrated tolerability of IV doses up to 1,260 mg with dose-proportional pharmacokinetics. A separate Phase 1 in 84 Chinese volunteers (Wang et al., 2021) confirmed safety of recombinant Tβ4 at 0.05–25 µg/kg. Phase 2 trials in venous stasis ulcers showed accelerated wound closure with topical 0.03% Tβ4 gel. The RGN-259 ophthalmic formulation has completed Phase 2 and entered Phase 3 for dry eye and neurotrophic keratitis. A cardiac STEMI pilot study suggested improved left ventricular function. Preclinical data spans wound healing, cardioprotection, neuroprotection, hair follicle activation, and anti-fibrotic effects via the Ac-SDKP domain. Community dosing protocols are extrapolated from these clinical trials and animal data.
Reported side effects
From community self-reports. Not from controlled studies.
Phase 1 trials (IV doses up to 1,260 mg) reported no serious adverse events. Community users report occasional injection site redness/swelling, mild headache, and transient fatigue at higher doses. Theoretical concern exists regarding angiogenesis promotion in individuals with pre-existing malignancies, though this has not been observed in clinical trials.
Regulatory status
FDA (United States)
Not approved. Category 2 — prohibited for pharmacy compounding (added October 2023). RGN-259 ophthalmic formulation holds orphan drug designation for neurotrophic keratitis and is progressing through the IND pathway (Phase 3).
Health Canada
Not authorized as a therapeutic product. No DIN assigned.
WADA (Competitive Athletes)
Prohibited at all times (in-competition and out-of-competition) under Section S2.3 — Growth Factors and Growth Factor Modulators. Explicitly named: 'Thymosin-β4 and its derivatives e.g. TB-500.' In effect since 2018 Prohibited List.
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